For some people 30 grand is day's income or couple of days income, or even less than days income.
Then look what 30 grand gets them...
a) Something other people with similar income will recognize from that he is their peer. Which is good for business.
b) Something that improves their chance of getting laid when trying to, as it both shows money and isn't too much of a showing off.
c) Good watch. People who have truckloads of money will probably try to get highest quality stuff since you don't enjoy that much of having million pairs of cheap socks, and thousand of cheap TV-screens, or thousand cheap watches in their basement. So what they can do with their money? Buy stuff that is far more expensive than what people consider almost as good. But as long as they think its higher quality its probably worth it for them because their time is really expensive for them.
I think b) is the thing what most slashdotters would gladly pay couple of days salary. While a) is probably most common reason to get that expensive watch.